- #1

lapo3399

- 55

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If the area under a curve is found for a function f(x)

[tex] A = \int_{a}^{b}\ f(x) dx [/tex]

which may also be represented as

[tex] A(x) = \int_{a}^{a+c}\ f(x) dx [/tex]

where h is the different between a and b, then

[tex] A(x) = F(a+c) - F(a) [/tex]

As A(x) will be maximized when the total area between the two roots is found (assuming no improper integrals or infinite areas), then

[tex] a(x) = f(a+c) - f(a)[/tex]

[tex] 0 = f(a+c) - f(a)[/tex]

[tex] f(a) = f(a+c)[/tex]

It is rather obvious that this means that the function has equal values (0 as the two x values lie on the x-axis) at f(a) or the first root and f(a+c) or the second root, but I must ask something that has been puzzling me concerning this rather meaningless conclusion : if the fact that the area function is maximized causes f(a) to equal f(a+c), and considering the fact that, for example, a quadratic has an infinite number of solutions for f(a) = f(a+c) that are not restricted to the roots of the equation, why should the maximization condition be necessary to produce the equation f(a) = f(a+c)?

The best explanation that I have for this is that, assuming c is remaining constant, the rate of change in area on the left will be the negation of the rate of change on the right, and so there is no maximum for the area function AS I have defined it. That is, if I were to take a quadratic and decrease a, the area concerned would increase/decrease by a certain amount, but the change in a+c would compensate for this with an equal area change on the right, thus keeping the area constant. The only way I see of defining this better is defining c as a non-constant, as it obviously will change depending on the function.

Please provide any insight that you have!

Thanks,

lapo3399